1. Field of the Invention
The invention relates in general to a touch control system, and more particularly, to a technique for implementing touch control by single-layer electrodes.
2. Description of the Related Art
Operating interfaces of recent electronic products have become more and more user-friendly and intuitive as technology advances. For example, via a touch screen, a user can directly operate programs as well as input messages/texts/patterns with fingers or a stylus; in this way, it is much easier to convey commands than operating via traditional input devices such as a keyboard or buttons. In practice, a touch screen usually comprises a touch sensing panel and a display device disposed at the back of the touch sensing panel. According to a position of a touch on the touch sensing panel and a currently displayed image on the display device, an electronic device determines an intention of the touch to execute corresponding operations.
Current touch control techniques are in general categorized into resistive, capacitive, electromagnetic, ultrasonic and optic types. The capacitive touch control technique can further be categorized into self capacitive and mutual capacitive types. In contrast to a mutual capacitive touch panel, although being implementable by a simpler single-layer electrode structure, a self capacitive touch panel falls short in supporting multi-touch control. Consequently, a mutual capacitive touch panel provides a far broader application scope than a self capacitive touch panel.
FIG. 1 shows a mutual capacitive touch panel according to the prior art. A plurality of transparent sensing wires, arranged in a matrix, are disposed at the back of the touch sensing panel. In this mutual capacitive touch panel, the sensing wires in an X direction are driving lines whereas the sensing wires in a Y direction are sensing lines. With reference to FIG. 1, each of the driving lines is connected to a driver 12, and each of the sensing lines is connected to a receiver 14. Generally, the drivers 12 sequentially send driving signals, and the receivers 14 continuously receive sensing signals. When a valid touch takes place, capacitance coupling occurs across the driving line and the sensing line corresponding to the touch point, resulting in a change in the corresponding sensing signal (e.g., a voltage value) associated with a mutual capacitance. According to the receiver 14 which detects the change in the sensing signal and the driver 12 which sends out the driving signal at the time of the touch, a subsequent circuit determines coordinates of the touch point with respect to the X and Y directions.
Conventionally, driving lines and sensing lines are respectively transparent electrodes disposed on different planes. FIG. 2A shows a diagram of a currently prevalent rhombus electrode pattern. Dark-shaded rhombus electrodes 16 having the same Y coordinate are serially connected to one another to form driving lines in the X direction; lightly-shaded rhombus electrodes 18 having the same X coordinate are serially connected to one another to form driving lines in the Y direction. It should be noted that the dark-shaded rhombus electrodes 16 and the lightly-shaded rhombus electrodes 18 are located on different planes, and parts of the two types of electrodes appearing as overlapping in the diagram are physically unconnected.
To reduce material costs, many manufacturers compress the foregoing double-layer electrode structure to a single-layer electrode structure. In a conventional single-layer electrode structure, principal rhombus electrodes of the dark-shaded rhombus electrodes 16 and the lightly-shaded rhombus electrodes 18 are formed on a same plane. Referring to FIG. 2B showing a top view of the single-layer electrode structure in FIG. 2A, parts of the two types appearing as overlapping in the diagram are implemented as three-dimensional bridge structures. In this example, a connecting line between two dark-shaded rhombus electrodes 16 is located on a same plane as the principal rhombus electrodes; a connecting line between each two lightly-shaded rhombus electrodes 18 is elevated to be in fact above the plane—as indicated crossing over the dark connecting line in the diagram. It is observed from the diagram that the conventional single-layer electrode structure is substantially not a real single-layer structure. Due to complex manufacturing procedures and a low yield rate of the foregoing three-dimensional bridge structures, the implementation of the current single-layer electrode structure may increase overall manufacturing complications and costs instead.
Moreover, the drivers 12 and the receivers 14 are frequently disposed in a circuit chip connected to a printed circuit board in a sensing panel. As the number of driving/receiving channels coupling the sensing panel and the circuit chip grows, the number of pins of the circuit chip also increases to result in even higher production costs.